Pups in tow, Yellowstone-area wolves trek long distances to stay near prey

 

For the first time, a UC Berkeley-led research team has observed gray wolves outside of the Arctic migrating during pup-rearing season

Peer-Reviewed Publication

University of California - Berkeley

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In a new study, a UC Berkeley-led team of biologists observed gray wolves near Yellowstone National Park traveling 20 kilometers or more over rugged, mountainous terrain, with very young pups in tow. It is the first time gray wolves outside of the Arctic have been observed migrating, or shifting their territorial range, to be closer to prey during pup-rearing season. This photo from the Thorofare Wilderness on the southeast side of Yellowstone National Park shows the summer range of one of Yellowstone’s migratory elk herds.

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Credit: Avery Shawler

Berkeley — Gray wolf pups are born nearly helpless: blind, deaf and lacking the acute sense of smell of their elders. They usually remain in the safe confines of their den until they are at least three weeks old.

That is why UC Berkeley biologists were surprised to observe gray wolves near Yellowstone National Park traveling 20 kilometers or more over rugged, mountainous terrain, with very young pups in tow. 

“The first time I saw a camera trap photo of a wolf carrying its pup, I just cracked up because the pup is being carried by its butt,” said Avery Shawler, first author of a new study presenting the findings, which appeared online today (Aug. 1) in the journal Current Biology. “You can picture a squirming child and the mom just being like, ‘All right, we're doing this.’”

Shawler and the other researchers believe wolves undertook these risky journeys to move their packs closer to elk, their preferred prey, during the elk spring migration to higher altitudes. The study is the first time gray wolves outside of the Arctic have been observed migrating, or shifting their territorial range, to be closer to prey during pup-rearing season. 

“Our findings counter years of assumptions by researchers that migratory hoofed mammals can escape predation in spring because [their predators] are tied to dens and immobile offspring,” said study senior author Arthur Middleton, a Berkeley professor of environmental science, policy and management.

Understanding how wolves are adapting to the movements of their prey is key to the conservation of both species, Shawler said. It can help land managers understand seasonal patterns of human-wildlife conflict in an ecosystem that includes both ranches and wilderness, where wolves may view livestock as a tasty alternative to elk. 

“In the U.S., more wolves live outside of protected areas than within protected areas, and these wolves are going to overlap with humans and livestock,” said Shawler, who completed a Ph.D. at UC Berkeley in 2024. “Our research provides some insight into the behavior of wolves living on working landscapes and how they've had to adapt to an environment that is different from what wolves were dealing with 100 years ago.”

Gray wolves were reintroduced to Yellowstone National Park in 1995, and researchers estimate that their population in the Greater Yellowstone Ecosystem has since grown to around 500. Tens of thousands of partially migratory elk also inhabit the region. 

Climate change and shifts in land use are putting pressure on both species and leading them to adapt accordingly. Earlier research led by Middleton showed that the timing of annual elk migrations is currently in flux, with elk arriving at their winter ranges up to 50 days later in 2015 compared to 2001.

To explore how elk migration patterns impact wolf behavior, the researchers used GPS collars to track the movements of 19 gray wolves and 99 elk in the eastern Greater Yellowstone Ecosystem between 2019 and 2021. 

They found that wolves are surprisingly adaptable to the movements of their prey. Some elk herds in Yellowstone only migrate short distances in the spring, and the wolf packs that tracked them generally stayed in the same territory where they first established their dens. Other elk herds travel much longer distances in the spring, and wolf packs that tracked them had to get more creative, engaging in behaviors the researchers called “commuting” and “migrating.”

The researchers used the term “commuting” to describe temporary forays taken outside of the wolves’ home territories, usually to track migrating elk herds. 

Wolves “migrated” when they moved to an entirely new seasonal range, following migrating elk up to 50 km. Sometimes they carried small pups as far as 20 km from their original dens to new pack “rendezvous” sites. 

“In Yellowstone, research has shown how a lot of wolf mortality can come from other packs coming in and killing pups, because there's a lot of packs competing for space and food,” Shawler said. “It's pretty wild that this risky behavior of moving young pups is even occurring when that's happening next door.”

The findings can inform conservation efforts and land management in any region that has gray wolves — including California, which is home to approximately 10 packs after wolves began recolonizing the state in 2011. Middleton is co-leading the new California Wolf Project, which aims to understand the social and ecological factors that are shaping these wolf populations.

“While it’s still early days, our partners in California have a strong hunch that the numbers and movements of deer and elk are playing into wolf behavior, including livestock predation,” Middleton said. “The work around Yellowstone sharpens our ideas and approaches as we grow the project in California.”

Additional study co-authors include Kristin J. Barker of UC Berkeley and Beyond Yellowstone Living Lab; Wenjing Xu of the Senckenberg Biodiversity and Climate Research Centre in Germany; and Kenneth J. Mills and Tony W. Mong of the Wyoming Game and Fish Department.

The study was supported by the National Geographic Society, Knobloch Family Foundation, George B. Storer Foundation, the Wyoming Game and Fish Department, UC Berkeley, and the USDA National Institute of Food and Agriculture, and conducted from a base at the Buffalo Bill Center of the West in Cody, Wyoming.

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Journal

Current Biology

DOI

10.1016/j.cub.2025.07.015 

Wildlife show wide range of responses to human presence in U.S. national parks

 

The presence of humans and human infrastructure in U.S. national parks has lasting effects on the behaviours of the large animals that call them home, according to a new study.

“Wildlife all around the world fear people and avoid areas of high human activity, but it was surprising to see that this holds true even in more remote protected areas,” said Dr. Kaitlyn Gaynor, a zoologist at the University of British Columbia and lead author of the paper published today in the Proceedings of the Royal Society B.

Researchers tracked 229 animals from 10 species across 14 national parks and protected areas using GPS collar data from 2019 to 2020, allowing them to study how animals navigated hotspots of human activity in parks before and during the COVID “Anthropause”. Species included grey wolves, mountain lions, black and grizzly bears, moose, mountain goats and bighorn sheep.

While overall, animals tended to avoid infrastructure such as roads, trails, parking lots, buildings and campgrounds, closer analysis showed responses varied across populations, species and individual animals. “This study reveals not only how wildlife respond to human presence but also why species respond differently, and the complex ways that animals balance risks and benefits associated with humans,” said co-author Dr. Forest Hayes, postdoctoral fellow at Colorado State University.

“Some species are just more wary of people than others, like bighorn sheep and mountain lions, while others have learned to associate humans with some benefit,” said Dr. Gaynor. “The mule deer and elk in Zion National Park prefer being closer to developed areas and around humans. That could be because their predators might be avoiding people, so if deer and elk can learn to live with us, they can reduce the risk of becoming prey.”

Avoidance even during lockdown

The researchers found animals in more developed areas switched from avoiding human infrastructure when the park was open in 2019 to using it more when the park was closed in 2020. Without any people around, animals were apparently more willing to explore the developed areas of the park.

 

“We heard from managers in Yosemite National Park that when people came back, the black bears stayed, which caused a lot of problems because the bears got used to the abundant food in Yosemite Valley and didn't want to give it up,” said Dr. Gaynor.

But in most other parks, avoidance of human infrastructure persisted even during the lockdowns. “While some individuals and populations showed a strong response to the absence of people during park shutdowns, most did not,” Dr. Gaynor said. “Because a lot of headlines in 2020 implied that animals were taking back our national parks and were on the streets everywhere, we expected to see a bigger effect. But it takes just a few individuals to start changing their behaviour to create the perception of a larger impact.”

The researchers speculate that due to the relatively short duration of park closures—an average of 58 days —many animals may not have had enough time to perceive and respond to the change in human activity, particularly those with low exposure to human development in their home ranges. Additionally, risk-averse individual animals and species may have already been displaced prior to the pandemic, while those animals with a high exposure to humans were already habituated.

Balancing recreation and conservation

Human presence influences both the resources available to animals and the risk of using those spaces, with differing effects on animal species. The responses of animals may shape which species eat and compete with each other, changing ecological dynamics, the researchers say. These responses may also affect the ability of animals to persist alongside people in protected areas.

U.S. national parks, which hosted over 327 million visits in 2019, balance the dual mandates of human recreation and wildlife conservation.

“Yellowstone National Park, Yosemite National Park and the Grand Canyon are international destinations that are crowded at peak times of year, but the crowds are concentrated near the roads and visitor centres and parking lots,” said Dr. Gaynor. “The study provides evidence that conservation is compatible with recreation at low levels but that we do need to keep some areas exclusively for wildlife.”

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Journal

Proceedings of the Royal Society B Biological Sciences

DOI

10.1098/rspb.2025.1013 

Yellowstone aspen showing signs of recovery following 1995 reintroduction of wolves to park

 

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Oregon State University researchers have documented the first new generation of overstory aspen trees in Yellowstone’s northern range in 80 years, three decades after wolves were reintroduced to the nation’s oldest national park. Photo provided by Luke Painter, OSU College of Agricultural Sciences.

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Credit: Photo provided by Luke Painter, OSU College of Agricultural Sciences.

Yellowstone National Park is celebrating an ecological milestone along with a key anniversary this summer, Oregon State University researchers report.

A paper published today in Forest Ecology and Management documents the first new generation of overstory aspen trees in Yellowstone’s northern range in 80 years, three decades after wolves were reintroduced to the nation’s oldest national park.

Without predation pressure from wolves, which had been extirpated from the park by 1930, elk populations grew to the point that their browsing was thwarting the growth of young aspen. The ecosystem effects were widespread as aspen stands support a range of species including beavers and cavity-nesting birds.

With wolves back in the mix along with bears and cougars, a nearly extirpated predator whose numbers increased along with wolf reintroduction, elk numbers have been reduced and aspen are once again working toward becoming full-grown trees.

 “The reintroduction of large carnivores has initiated a recovery process that had been shut down for decades,” said the study’s lead author, Luke Painter, who teaches ecology and conservation in the OSU College of Agricultural Sciences. “About a third of the 87 aspen stands we examined had large numbers of tall saplings throughout, a remarkable change from the 1990s when surveys found none at all.”

Another third of the surveyed stands had patches of tall saplings growing into new overstory trees, he added, and the rest remained suppressed by herbivory.

“Increasing numbers of bison may be emerging as a new constraint to aspen in some areas,” Painter said.

The fact that stands with many tall saplings have low rates of browsing, whereas other stands continue to be suppressed, indicates aspen recovery is happening because of a trophic cascade and not other factors such as climate or site productivity, he said.

In a trophic cascade, a change at the top of a food web causes ripple effects throughout an ecosystem, altering its structure and balance. In Yellowstone, top predators have reduced herbivory by elk, allowing aspen to begin to recover.

“This is a remarkable case of ecological restoration,” Painter said. “Wolf reintroduction is yielding long-term ecological changes contributing to increased biodiversity and habitat diversity.”

Collaborating with Painter were Robert Beschta and William Ripple of the OSU College of Forestry. The Ecosystem Restoration Research Fund of the Oregon State University Foundation supported the research.

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Journal

Forest Ecology and Management

DOI

10.1016/j.foreco.2025.122941 

Coastal Alaska wolves exposed to high mercury concentrations from eating sea otters

 

In late 2020, a female coastal wolf collared for a study on predation patterns unexpectedly died in southeastern Alaska. 

The wolf, No. 202006, was only four years old. 

“We spent quite a bit of time trying to figure out the cause of her death by doing a necropsy and different analyses of tissues,” says Gretchen Roffler, a wildlife research biologist with the Alaska Department of Fish and Game.

“What finally came up was really unprecedented concentrations of mercury in this wolf’s liver and kidneys and other tissues.”

Roffler was put in touch with Dr. Ben Barst, PhD, an assistant professor in the Faculty of Science at the University of Calgary who was working at the University of Alaska Fairbanks at the time.

They, along with a team of other scientists, have now published new research in the journal Science of The Total Environment that shows wolves eating sea otters have much higher concentrations of mercury than those eating other prey such as deer and moose.

Mercury found in high concentrations in predators

Barst, an expert in ecotoxicology, says mercury is a naturally occurring element humans release from the Earth’s crust through coal combustion and small-scale gold mining.

“It’s a really weird metal in that it’s liquid at room temperature or it can be a vapour,” he says. “When it gets into the atmosphere in its elemental form, it can travel for really long distances.”

Barst says it also gets converted into methyl mercury when it gets into aquatic environments.

“It’s an organic form of mercury that really moves quite efficiently through the food web, and so it can reach high concentrations in predators that are tapped into aquatic food webs," he says. "So, we see higher concentrations in wolves that are tapped into a marine system.”

The latest research compares wolves from Pleasant Island — located in the Alaska Panhandle region, west of Juneau — with the population on the mainland adjacent to the island, as well as wolves from interior Alaska.

“The highest concentrations are the wolves from Pleasant Island,” says Barst, noting that the mainland population mostly feeds on moose and the odd sea otter.

He says there could be a number of factors driving the higher concentrations of mercury, but they are still researching several possibilities. 

Mercury-wolf health impact examined

Researchers are also doing more work to determine mercury’s role in impacting wolf health, as it remains unclear exactly what caused the death of Wolf No. 202006.

Barst notes, however, that years of data collected by Roffler show that 70 per cent of the island wolves’ diet is sea otters.

“They're eating so many sea otters that they're just getting this higher dose of mercury and it accumulates over time,” he says.

Roffler says there are other populations of wolves in Alaska as well as in B.C. that appear to be eating sea otters.

“It turns out that this might be a more widespread phenomenon than we thought originally,” she says. “At first I was surprised it was happening at all.”

It’s not yet known whether the sea otters off the B.C. coast also contain high levels of mercury.

Potential link to climate change

Back in Alaska, Barst says there’s a potential link to climate change due to the state's shrinking glaciers.

“We know that glaciers can release a tremendous amount of mercury,” he says. “In coastal Alaska, glaciers are retreating at some of the most rapid rates in the world.

“With that melting of glaciers, you get release of the particulate bedrock and some of that bedrock contains mercury – and so we don’t really know the fate of that mercury. It may just get buried in sediments or it may actually be available for conversion to methyl mercury and get into the food web.

“That’s part of what we’re doing now.”

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Journal

Science of The Total Environment

DOI

10.1016/j.scitotenv.2025.179542 

Who decides on removing grizzly bears from the endangered species list?

Guest editorial by Dr Kelly Dunning, Timberline Professor of Sustainable Tourism and Outdoor Recreation at the University of Wyoming

Peer-Reviewed Publication

Frontiers

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Dr Kelly Dunning's research focuses on biodiversity conservation and the human dimensions of natural resources in tourism prone areas.

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Credit: Kelly Dunning

By Dr Kelly Dunning

The Endangered Species Act (ESA), now 50 years old, was once a rare beacon of bipartisan unity, signed into law by President Richard Nixon with near-unanimous political support. Its purpose was clear: protect imperiled species and enable their recovery using the best available science to do so. Yet, as our case study on the grizzly bear in the Greater Yellowstone Ecosystem reveals, wildlife management under the ESA has changed, becoming a political battleground where science is increasingly drowned out by partisan ideology, bureaucratic delays, power struggles, and competing political interests. The survival of the ESA, a wildlife policy mimicked all over the world, may depend on our ability to navigate these waters.

The grizzly bear, a cultural symbol of the American West, embodies this shift. Listed as threatened in 1975 when its numbers dwindled to fewer than 1,000 and its range contracted by 98%, the species has managed to come back from the brink. In the Greater Yellowstone Ecosystem, the population now exceeds 700, a number that surpassed recovery goals set by the federal wildlife management agency tasked with recovery, the US Fish & Wildlife Service. By the ESA’s own metrics, this is a success story, which now means the grizzly bear is eligible for ‘delisting’. Yet, attempts to remove federal protections in 2007 and 2017 were overturned by courts, not because the science was lacking, but because the process has become a lightning rod for political interests.

Our study looks at 750 documents and 2,832 stakeholder quotes to track this politicization. Historically, wildlife management is the strict domain of agency scientists in the executive branch. These scientists are experts trained to interpret interdisciplinary scientific data and balance both human and ecological needs.

Our work shows that today, the most dominant voices belong to legislators, legal advocates, and non-governmental organizations (NGOs) who are increasingly crowding out the agency scientists. Senators, elected politicians, like Wyoming’s John Barrasso proclaim, “The grizzly is fully recovered in Wyoming. End of story,” pushing for state control and criticizing the ESA as sluggish and outdated. Can you blame him though? Senator Barraso advocates for his Wyoming constituents who have collaborated in grizzly recovery and are now on the frontlines of human-wildlife conflict issues where grizzlies might harm livestock or tourists. All the while, population targets set by the ESA have been met, and the species remains listed.

Meanwhile, NGOs and their attorneys, such as the well-known environmental advocacy group Earthjustice, argue that delisting is premature, citing ‘political pressure’ overriding ‘biological evidence.’ The courts, too, have flexed their muscle, with rulings hinging on genetic connectivity’s role in population recovery. Ranchers with increasing grizzly conflict see these scientific developments as intentional delays to delisting rather than advancements in the field of conservation. There are no easy answers.

Wildlife management turned politics

This conflict reveals a stark reality: wildlife management is no longer just about science, it's about who dominates the political discourse, and the power that accompanies it. Legislators see delisting as a way to reclaim state authority from what they consider federal overreach. Their rhetoric, steeped in populist appeals to the Western ranching community, frames grizzlies as a recovered species with bureaucrats in Washington stalling the process of handing management back over to the states.

Montana Senator Steve Daines, for instance, highlights ‘skyrocketing’ livestock losses and bears roaming beyond their historic range. These issues resonate with rural constituents tired of federal wildlife law superseding local management by trusted state agencies. On the other hand, NGOs and legal advocates rely on the courts to maintain federal oversight, warning that state management could unleash ‘trigger-happy’ hunting seasons and jeopardize long-term survival. These advocates argue that we are facing a generational extinction crisis, where every decision we make about imperiled species could approach extinction, a route that we cannot come back from. The public, caught in the middle, may be unaware that conversations over wildlife protection have shifted from credentialed agency biologists and scientists over to politicians.

Our data underscore this shift in power. While executive branch officials, with whom scientific expertise resides, once dominated the discourse (eg fish and wildlife agency personnel at the federal and state level), they are no longer the leading voices in ESA recovery conversations. Elected politicians now lead the charge. Their influence is growing threefold over time compared to scientific agency voices. Legal advocates and NGOs, meanwhile, are shaping the debate over wildlife science with their roles amplified by lawsuits that keep grizzlies listed. Even tribes, historically sidelined, find their strongest platform in court, a sign that political systems still fail to integrate Indigenous perspectives outside litigation.

What’s lost in this debate is the ESA’s original intent: a science-driven process to recover species and then allow federal agency experts to step back so that states, who may better represent local interests, can manage species.

The path forward

This politicization threatens the ESA’s future. When politicians outshout scientists, when courts dictate biology or delay timely management responses, and when recovery becomes a bargaining chip, the law risks losing its credibility with the public. The grizzly saga suggests a path forward: agencies must adapt to this political reality, not retreat from it. Scientists can’t afford to ‘stay out of politics’ when protected species like grizzlies are lightning rods for political debate. Multi-stakeholder groups, like the Interagency Grizzly Bear Committee, offer a model bridging agencies, states, tribes, and NGOs to tackle thorny issues like genetics collaboratively rather than through unending lawsuits in the courts.

The grizzly bear’s fate isn’t just about one species: this pattern is playing out across a range of species in the West and beyond. It will prove itself as the greatest challenge for wildlife managers in an era of increased polarization. If the ESA is to endure another 50 years, it must evolve beyond a scientific ideal into a framework that navigates the messy, human politics of conservation. Otherwise, the grizzly’s roar will be drowned out by an even greater sound: the chaos of our own imperfect politics.

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Journal

Frontiers in Conservation Science

DOI

10.3389/fcosc.2025.1508158 

 

Wolves make a rapid recovery in Europe

 

Peer-Reviewed Publication

PLOS

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Wolf on agricultural plains in northern Greece

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Credit: Seryios Papaioannou, CC-BY 4.0 (https://creativecommons.org/licenses/by/4.0/)

 Wolf populations in Europe increased by nearly 60% in a decade, according to a study led by Cecilia Di Bernardi and Guillaume Chapron at the Swedish University of Agricultural Sciences, published in the open-access journal PLOS Sustainability and Transformation.

Large carnivore populations are declining worldwide. However, in Europe, conservation policies have supported the recovery of wolves (Canis lupus) in recent decades. To understand current trends in their populations, researchers collated data on wolf numbers in 34 countries across Europe. They found that by 2022, at least 21,500 wolves lived in Europe — an increase of 58% compared to the estimated population of 12,000 a decade earlier. In most countries analyzed, wolf populations were increasing, with only three countries reporting declines over the previous decade. The researchers also investigated sources of conflict between humans and wolves, such as livestock deaths. They estimated that in the European Union, wolves killed 56,000 domestic animals per year, out of a total population of 279 million livestock. Although the risk varied between countries, on average, livestock faced a 0.02% chance of being killed by wolves each year. Compensating farmers for these losses cost European countries 17 million euros annually. Still, wolves can also have positive economic impacts, such as reducing traffic accidents and damage to forestry plantations by controlling wild deer populations. However, there wasn’t enough data available to quantify these benefits.

Considering Europe’s large human population and the widespread alteration of landscapes for agriculture, industry and urbanization, the rapid recovery of wolves over the last decade highlights their extraordinary adaptability. However, as conservationists transition from saving endangered populations to sustaining a successful recovery, the challenge will be to adapt national and international policies to ensure that humans and wolves can coexist sustainably in the long term, the authors say. 

The authors add: “The recovery of wolves across human-dominated landscapes of Europe has been continuing during the past decade, with their population growing to over 21,500 individuals by 2022 – a 58% increase in a decade. Ongoing and future challenges include damages directly caused by wolves and broader socio-political issues.”

The freely available article in PLOS Sustainability and Transformation:  https://plos.io/41wNLjq